The Australian Transport Safety Bureau (ATSB) is Australia's national transport safety investigator. The ATSB's function is to improve safety and public confidence in the aviation, marine and rail modes of transport. The ATSB is Australia's prime agency for the independent investigation of civil aviation, rail and maritime accidents, incidents and safety deficiencies.

Interim No.1

Summary

Interim Factual report No.1 released 6 March 2009

At 0932 local time (0132 UTC) on 7 October 2008, an Airbus
A330-303 aircraft, registered VH-QPA, departed Singapore on a
scheduled passenger transport service to Perth, Australia. On board
the aircraft (operating as flight number QF72) were 303 passengers,
nine cabin crew and three flight crew. At 1240:28, while the
aircraft was cruising at 37,000 ft, the autopilot disconnected.
From about the same time there were various aircraft system failure
indications. At 1242:27, while the crew was evaluating the
situation, the aircraft abruptly pitched nose-down. The aircraft
reached a maximum pitch angle of about 8.4 degrees nose-down, and
descended 650 ft during the event. After returning the aircraft to
37,000 ft, the crew commenced actions to deal with multiple failure
messages. At 1245:08, the aircraft commenced a second uncommanded
pitch-down event. The aircraft reached a maximum pitch angle of
about 3.5 degrees nose-down, and descended about 400 ft during this
second event.

At 1249, the crew made a PAN urgency broadcast to air traffic
control, and requested a clearance to divert to and track direct to
Learmonth. At 1254, after receiving advice from the cabin of
several serious injuries, the crew declared a MAYDAY. The aircraft
subsequently landed at Learmonth at 1350.

One flight attendant and 11 passengers were seriously injured
and many others experienced less serious injuries. Most of the
injuries involved passengers who were seated without their
seatbelts fastened or were standing. As there were serious
injuries, the occurrence constituted an accident.

The investigation to date has identified two significant safety
factors related to the pitch-down movements. Firstly, immediately
prior to the autopilot disconnect, one of the air data inertial
reference units (ADIRUs) started providing erroneous data (spikes)
on many parameters to other aircraft systems. The other two ADIRUs
continued to function correctly. Secondly, some of the spikes in
angle of attack data were not filtered by the flight control
computers, and the computers subsequently commanded the pitch-down
movements.

Two other occurrences have been identified involving similar
anomalous ADIRU behaviour, but in neither case was there an
in-flight upset.